I like Hero Siege. I like D&D. Thus, I go 'Why not cross the two a bit?' And so this is my first thing I try. Bring it over, make it worthy of the artifact label. Might be a bit much? At least the DM always controls artifacts.
In Hero Siege, is is a passive relic that gives your character a disgusting amount of strength, but sharply decreases your other stats.

Damien's Amulet
Wondrous Item, artifact (requires attunement)
Damien's Amulet goes by many names, but this is the most commonly known. Rumoured to grant those who wear it incredible strength, but at great cost, some choose to hunt it regardless. Described as a necklace with a chain of black, a round plate with a pentagram of red etched upon it, there is no doubt this is one of the evillest artifacts thought to exist.
It is believed that some great evil, from long ago created this amulet to corrupt mortals. Those who claim to have found it agree with this, saying that the amulet whispers vile desires to them. The stronger the owner, they say, the worse it becomes.
Most die horribly at some point in their lives, insisting the amulet won't leave them alone. Whether by their own hand, or monsters.

This artifact will not attune to someone who is already Evil, as you have nothing to offer it in turn.

Power at a Price. This artifact, when worn, damages your mind and body even as it grants you the power you so desire.
You lose 3 to each ability score
You gain 13 Strength or Intelligence, up to a cap of 30. This can only be decided upon attuning, and never again.
Your alignment shifts one closer to Evil so long as it is attuned. This will not cause it to unattune if it shifts your alignment to Evil.

Fiendish Ally. Once per day, you may cast Planar Ally. This casting may only be used to summon a Fiend.
This power refreshes at Midnight exact.

Dark Whispers. Each day, at any point, the Amulet will whisper to its owner terrible desires. The wearer must make a Wisdom save equal to their level, plus the number of times they have resisted the Amulet in a row thus far.* If they fail, they must carry out the demand to the best of their ability. The Amulet will never tell them to attack or otherwise directly harm a friend or themselves, though it will always tell them to do some evil act. Typically, this act will benefit the owner.
Should they make the save, it will still tell them its desire. Completing this desire, willingly or not, will cause the Amulet to provide subtle advice for the remainder of the day.
(DC=N+R, N being level and R being times resisted in a row. Example: Level 10, resisted twice, DC12 save.)

Death do us Apart. Once attuned, the Amulet may never be truly rid of. Unless the owner actively casts it away with hopes to never see it once more, it will always find its way back. Within 1d4 days of being lost or abandoned, the owner will find the Amulet within their belongings. Upon it returning, they take an amount of Psychic damage equal to their level d4*, as the amulet violently berates them and their soul for abandoning it.
Unless actively worn, the Amulet is silent and does not provide any of its advantages. The attribute penalty, detrimental properties, and alignment change remain.
(* Nd4, where N being level)

Destroying the Amulet. To be rid of the Amulet merely requires the owner to cast it away, yelling some variation of them hoping to never see it again. This will leave the Amulet distraught, and it will go into hiding for 2d4-1 months unless someone else immediately claims it. At the end of this, it will re-emerge somewhere, but never again for someone who has left its vile heart broken.
The previous owner will retain the attribute damage until it re-emerges, or magic is used to restore them. All other effects disappear immediately.
To truly destroy it is a much trickier matter. It must be worn by the greatest evil to exist at the time. Upon the chains being attached around this evil's neck, the amulet will shatter forever.

...so, is it awful? Please be honest. The backstory is short because there was nothing to go off of.
Also I just realised that the way to be rid of it is as if breaking up with an abusing significant other. Heh.